1. Field of the Invention
The present invention relates to an illuminating device for illuminating an irradiation target such as an original, an image-reading apparatus provided with the illuminating device, and image-forming apparatus provided with the image-reading apparatus.
2. Description of Related Art
This type of illuminating device is used mounted on, for example, an image-reading apparatus, is provided with a plurality of light-emitting elements (e.g., LEDs) that are arranged in a line parallel to a main-scanning direction for reading an original, and illuminates an original using these light-emitting elements. The image-reading apparatus repeatedly scans an original illuminated by the illuminating device in the main-scanning direction, and, at the same time, scans the original also in a sub-scanning direction, thereby reading the entire original. An image of this read original is output to a printer or the like, and recorded on a recording paper.
In such an illuminating device, all parts of light emitted from each light-emitting element are desirably caused to be incident on an original reading range. However, actually, all parts of light emitted from each light-emitting element cannot be caused to be incident on the original reading range, and a light loss occurs. There is a demand for reduction in this light loss.
Thus, in JP 2008-35036A, each light-emitting element and a light guide are mounted on a base material, the light guide is positioned on the light-emitting side of each light-emitting element, light from each light-emitting element is condensed by this light guide and emitted to the original reading range, and light that does not pass through the light guide is reflected by a reflecting plate and emitted onto the original reading range, thereby achieving a reduction in the light loss.
In JP 2008-35036A, light that does not pass through the light guide is reflected by the reflecting plate and emitted onto the original, but the light from the light-emitting elements is dispersed light. Thus, all parts of the light cannot be caused to be incident on the reflecting plate, and the light loss cannot be sufficiently reduced. In particular, the orientation of light emitted from the light-emitting elements in a direction substantially parallel to the base material surface is not controlled at all, and a reduction in the light loss of this light is not achieved.